Charge transport processes in nonconjugated redox-active polymers with electrolytes were studied using a diffusion-cooperative model. For the first time, we quantitatively rationalized that the limited Brownian motion of the redox centers bound to the polymers resulted in the 10-fold decline of the bimolecular and heterogeneous charge transfer rate constants, which had been unexplained for half a century. As a next-generation design, a redox-active supramolecular system with high physical mobility was proposed to achieve the rate constant as high as in free solution system (>10 M s) and populated site density (>1 mol/L).

Figure 4. a) Photographs of P1/SWNT (9:1 w/w)electrodes. b) Charge/discharge curves of the quasi-solid-state cell (specific capacity of P1 is shown).

A supramolecular gelator, 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO)-substituted cyclohexanediamine derivative, was synthesized, and its excellent charge-transporting capability was explored. The gels with organic solvents and electrolytes, or with ionic liquids, were formed via reversible sol–gel phase transition at ca. 50 °C. The organogels displayed electrochemical redox responses at E 1/2 = 0.72 V (vs Ag/AgCl) ascribed to the TEMPO moiety. Charge diffusion coefficient of the gel reached 3.3 × 10–7 cm2/s even in the quasi-solid state, which was comparable to those of the homogeneous solution (ca. 10–6). The high charge-transporting capability led to the tremendously large current density (a diffusion limited one) of ca. 1.0 mA/cm2 on a current collector and long distance for the charge-transporting beyond the organogel thickness of 50 μm. A half-cell of the organogel performed a plateau output voltage at the E 1/2, very high rate, and almost quantitative charging–discharging, and it had cyclability without any additives such as conductive carbons and binder polymers.

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